Arteriosclerosis is a condition where deposits build up along an inner surface of a blood vessel and cause a partial or, in extreme cases, a total blockage of the blood vessel. The increase in the number of coronary by-pass operations is some indication of the incidence with which the problem is encountered in older patients.
Prior art proposals recognize that one alternative to bypass-ing a partially or totally blocked region in a blood vessel is to open or widen the blocked blood vessel. One prior art technique for reopening a blocked blood vessel is to insert a balloon catheter inside the vessel to expand the vessel and either break loose deposits within the vessel or alternatively, increase the size of the lumen passing through those deposits.
An alternate proposal for opening a blocked blood vessel is to bring a high-speed rotating device into contact with occluded portions of the blood vessel. The rotating device produces cutting, abrading, or fluid turbulence to open the vessel and increase blood flow. One device intended for physically opening the blood vessel in this manner is disclosed in U.S. Pat. No. 3,614,953 to Moss entitled "Improvements In or Relating To Drills for Clearing Obstructions". In this patent, a high-speed motor rotates a flexible drive shaft connected to a cutting bit. The bit and flexible drive shaft are inserted into an occluded blood vessel so that when the bit is rotated at high speed and moved into contact with occluded regions it breaks loose deposits within the blood vessel.
A more recent prior art patent disclosing a similar system for opening a blocked blood vessel is disclosed in U.S. Pat. No. 4,445,509 to Auth entitled "Method and Apparatus for Removal of Enclosed Abnormal Deposits". This patent describes a differential cutting tool mounted at a distal end of a flexible shaft which can be inserted into an occluded blood vessel. Again, high speed rotation of the cutting tool causes the tool to remove abnormal deposits from inside the blood vessel.
U.S. Pat. No. 4,589,412 to Kensey entitled "Method and Apparatus for Surgically Removing Remote Deposits" discloses a procedure for removing atherosclerotic plaque. A cutting tip is rotated by the application of fluid pressure through a multi-lumen catheter.
U.S. Pat. No. 4,679,557 to Opie et al. entitled "Electrodynamic Transluminal Angioplasty System" discloses an advancer assembly that includes an off-axis drive that rotates a cutting tool such as that disclosed in the '509 patent to Auth.
The '509 patent to Auth stresses the importance in removing particles separated from an inner wall of the blood vessel. A hollow drive shaft is proposed by Auth to allow suction to be applied to a distal tip of the differential cutting tool disclosed in the '509 patent. It is suggested that particle-entrained blood will flow through the cutting tool to the hollow drive shaft when suction is applied.
USSR Pat. No. 778,067 to Yukhin discloses a helical cutter driven by a flexible shaft for separating blood clots from an internal blood vessel wall. A sheath surrounds the flexible shaft and is connected at a proximal location to a vacuum system for withdrawing separated clot particles from the blood vessel.
U.S. Pat. No. 3,732,858 to Banko discloses a system for removing blood clots, cataracts, and other objects from the eye. At FIG. 12 of this patent a cutting tip is driven by a solid, inflexible shaft having a "helical defining groove . . . such that it acts as a pumping means for removal of the material" (col. 15, lines 44-45) The use of an inflexible shaft makes the Banko system unsuitable for insertion into and passage through a patient's cardiovascular system.